// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2014-2019 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_INVERSE_H
#define EIGEN_INVERSE_H

namespace Eigen {

template <typename XprType, typename StorageKind> class InverseImpl;

namespace internal {

    template <typename XprType> struct traits<Inverse<XprType>> : traits<typename XprType::PlainObject>
    {
        typedef typename XprType::PlainObject PlainObject;
        typedef traits<PlainObject> BaseTraits;
        enum
        {
            Flags = BaseTraits::Flags & RowMajorBit
        };
    };

}  // end namespace internal

/** \class Inverse
  *
  * \brief Expression of the inverse of another expression
  *
  * \tparam XprType the type of the expression we are taking the inverse
  *
  * This class represents an abstract expression of A.inverse()
  * and most of the time this is the only way it is used.
  *
  */
template <typename XprType> class Inverse : public InverseImpl<XprType, typename internal::traits<XprType>::StorageKind>
{
public:
    typedef typename XprType::StorageIndex StorageIndex;
    typedef typename XprType::Scalar Scalar;
    typedef typename internal::ref_selector<XprType>::type XprTypeNested;
    typedef typename internal::remove_all<XprTypeNested>::type XprTypeNestedCleaned;
    typedef typename internal::ref_selector<Inverse>::type Nested;
    typedef typename internal::remove_all<XprType>::type NestedExpression;

    explicit EIGEN_DEVICE_FUNC Inverse(const XprType& xpr) : m_xpr(xpr) {}

    EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR Index rows() const EIGEN_NOEXCEPT { return m_xpr.cols(); }
    EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR Index cols() const EIGEN_NOEXCEPT { return m_xpr.rows(); }

    EIGEN_DEVICE_FUNC const XprTypeNestedCleaned& nestedExpression() const { return m_xpr; }

protected:
    XprTypeNested m_xpr;
};

// Generic API dispatcher
template <typename XprType, typename StorageKind> class InverseImpl : public internal::generic_xpr_base<Inverse<XprType>>::type
{
public:
    typedef typename internal::generic_xpr_base<Inverse<XprType>>::type Base;
    typedef typename XprType::Scalar Scalar;

private:
    Scalar coeff(Index row, Index col) const;
    Scalar coeff(Index i) const;
};

namespace internal {

    /** \internal
  * \brief Default evaluator for Inverse expression.
  *
  * This default evaluator for Inverse expression simply evaluate the inverse into a temporary
  * by a call to internal::call_assignment_no_alias.
  * Therefore, inverse implementers only have to specialize Assignment<Dst,Inverse<...>, ...> for
  * there own nested expression.
  *
  * \sa class Inverse
  */
    template <typename ArgType> struct unary_evaluator<Inverse<ArgType>> : public evaluator<typename Inverse<ArgType>::PlainObject>
    {
        typedef Inverse<ArgType> InverseType;
        typedef typename InverseType::PlainObject PlainObject;
        typedef evaluator<PlainObject> Base;

        enum
        {
            Flags = Base::Flags | EvalBeforeNestingBit
        };

        unary_evaluator(const InverseType& inv_xpr) : m_result(inv_xpr.rows(), inv_xpr.cols())
        {
            ::new (static_cast<Base*>(this)) Base(m_result);
            internal::call_assignment_no_alias(m_result, inv_xpr);
        }

    protected:
        PlainObject m_result;
    };

}  // end namespace internal

}  // end namespace Eigen

#endif  // EIGEN_INVERSE_H
